A radiological image detection apparatus using a Flat Panel Detector (FPD) that detects a radiological image to generate digital image data has recently been used practically. The radiological image detection apparatus may immediately confirm an image, as compared to a conventional imaging plate, and thus has been rapidly distributed. There are various types of radiological image detection apparatus, and as one of them, an indirect conversion type of the device is known.
The indirect conversion type of radiological image detection apparatus is provided with a radiological image conversion panel and a sensor panel having two-dimensionally arranged photoelectric conversion elements, in which the radiological image conversion panel has a scintillator formed of a fluorescent material that emits fluorescence through radiation exposure, such as CsI or GOS(Gd2O2S). Typically, the radiological image conversion panel and the sensor panel are bonded so that the scintillator is in close contact with the two-dimensional arrangement of the photoelectric conversion elements. Radiation passing through the subject is first converted into light by the scintillator of the radiological image conversion panel, and the fluorescence of the scintillator is photoelectrically converted by a group of the photoelectric conversion elements of the sensor panel to generate an electrical signal (digital image data).
As for the indirect conversion type of the radiological image detection apparatus, there has been suggested a radiological image detection apparatus of a so-called surface reading type (ISS: Irradiation Side Sampling) where radiation is allowed to be incident from the sensor panel side (for example, see Patent Literature 1). According to the radiological image detection apparatus, the amount of fluorescence emitted from the scintillator in the vicinity of the sensor panel is increased, thereby improving the sensitivity. This may reduce the exposure amount required for detecting a radiological image, thereby reducing the exposure dose of the subject.
Also, there is known a technology of forming a scintillator by a group of columnar crystals through a vapor deposition method so as to improve the sensitivity, in which the columnar crystals are obtained through columnar growth of crystals of a fluorescent material such as CsI on a support (for example, see Patent Literatures 2 and 3). The columnar crystals formed by the vapor deposition method do not include impurities such as a binding agent, and also has a light guide effect of guiding the fluorescence emitted therefrom in the growth direction of the crystals, thereby suppressing the diffusion of the fluorescence. Accordingly, the improvement in the sensitivity of a radiological image detection apparatus and the sharpness of an image may be achieved.
Further, in order to improve the characteristics of a radiological image conversion panel provided with a scintillator including a group of columnar crystals, various suggestions have been made. For example, in the radiological image conversion panel described in Patent Literature 2, a non-columnar section including a group of spherical crystals of a fluorescent material is formed at the support side of the scintillator, and thereon, a columnar section including a group of columnar crystals is formed. Since the non-columnar section is interposed between the support and the columnar section, the improvement in the adhesion of the scintillator with the support is achieved. Also, by the light reflection in the non-columnar section, the improvement of use efficiency of fluorescence, and thereby the improvement of the sensitivity may be achieved.
In the radiological image conversion panel described in Patent Literature 3, a non-columnar section including a group of spherical crystals of a fluorescent material is formed at the support side of the scintillator, and thereon, a columnar section including a group of columnar crystals is formed. The non-columnar section is structured in two layers and a spherical crystal layer where spherical crystals exist independently with each other is provided at the support side. And, a domain layer where a plurality of spherical crystals are aggregated to form a domain is formed at the columnar section. The spherical crystal layer mitigates a relatively small stress, and the domain layer mitigates a large stress such as a shear force, thereby improving the adhesion of the scintillator with the support.